1. Field of the Invention
This invention pertains to the packaging of electronic components and devices such as integrated circuit chips within chip-scale sized packages. More particularly this invention pertains to the packaging of acoustic wave devices and related components.
2. Description of the Prior Art
The development of very small electronic components and devices such as semi-conductor integrated circuits has given rise to the need for packages adapted for use with such small components and devices. Such packages typically must hold in place and contain such components and protect the components from harm from the environment, e.g. damage from mechanical contact, harmful electrical contact, and contact with harmful liquids and gases. The packages also usually must provide electrical connections to the components within the packages. Devices for high frequency operation must also be packaged such that the electrical connections to the device do not introduce detrimental parasitic effects.
A widely used, prior art package consists simply of the encapsulation of the integrated circuit chip, or die, within a plastic block of material, e.g. the ubiquitous rectangular solid block of plastic (dual in-line package "DIP") that has 14 or more external pins located along two sides of the block and contains a chip holding from 256 thousand to 256 million bits of random access memory. Typically, the integrated circuit chip is placed upon a lead frame and bond wires are connected between the chip and the lead frame. The chip and lead frame are then encapsulated in plastic. An alternate method of packaging is to place the die into a package having existing walls, sides and leads, connecting bond wires between the die and package lead pads and then attaching a lid to the package. Such packages, however, are unsuitable for use at microwave frequencies because the wire bond lead lengths give rise to excessive inductances and other parasitic effects that degrade device performance.
Surface acoustic wave devices and related devices such as thin film bulk-wave resonators have been developed for use with integrated circuit devices. The dice upon which these surface acoustic wave devices and resonators are fabricated typically are "chip-scale" in size, having dimensions of the order of a few millimeters in length and width and thicknesses of the order of one-quarter of a millimeter. Such chip-scale devices, however, cannot be packaged using the encapsulation technique described above, because the portion of the surface of the die that supports acoustic waves or the portion of the die that acts as an acoustic resonator must be free to deform or vibrate. If such acoustic devices were encapsulated, the portion of the die that supported the acoustic waves or that supported acoustic deformations or vibrations would be unable to deform or vibrate and the device would then be inoperable.
In a paper titled "A New All Quartz Package for SAW Devices", in the 39th Annual Frequency Control Symposium--1985, p. 519, Parker, Callerame and Montress disclose a package for a surface acoustic wave ("SAW") device that utilizes a quartz lid placed upon top of the substrate that contains the device, which lid is bonded to the substrate using a glass frit that provides a hermetic seal and offsets the lid from the acoustically active surface of the substrate. The electrical connections to the acoustic device, however are made via conductors located on the substrate that pass through, or under the glass frit. The quartz lid does not include electrical connections to the acoustic device. As a consequence, the packaging device described by Parker et al, is not adapted for surface mounting to a printed circuit board.